Standard included angle of lathe centres In general-purpose engine lathes, what is the standard included angle used for live and dead centres that support workpieces between centres?

Introduction / Context:
Turning between centres requires accurately ground centres on both the work and the lathe. The included angle of these centres must be standardized for compatibility and load-carrying capability.

Given Data / Assumptions:

• Conventional engine lathe with Morse taper live/dead centres.
• No special-purpose centres (e.g., carbide-tipped bull-nose) are considered.

Concept / Approach:
The widely adopted standard included angle for lathe centres is 60°. This angle offers a good compromise between seating area and self-centering capability, minimizing deformation while supporting axial and radial loads during turning.

Step-by-Step Solution:

Verification / Alternative check:
Machine tool standards, centre drill geometry, and inspection gages reflect the 60° convention for most turning operations.

Why Other Options Are Wrong:
30°/45°/90°/75°: nonstandard for general turning centres; would not match standard centre drills.

Common Pitfalls:
Confusing the included angle of centres (60°) with Morse taper angles used in spindles and tailstocks; these are unrelated geometric standards.

Final Answer:

60°